Primi risultati del monitoraggio con misure di velocità in un acquifero carsico costiero (Bari, Italia meridionale)

The study area is located in the Murgia plateau which constitutes a large and deep coastal karst aquifer (of Mesozoic age); the predominant rock material of which is either limestone or limestone-dolomite. The aquifer is affected by karst and fracturing phenomena, also well below the sea level, whereas intruded seawater underlies fresh groundwater owing to a difference in density. The groundwater flow is confined, except on a restricted coastline strip. A strong connection between the increase in salt contamination and the lowering of piezometric levels, which can be ascribed to groundwater overdraft and/or a natural decrease in groundwater recharge, has been recognised in the coastal area. To contribute to the study of this groundwater and quality degradation phenomena on the basis of affordable data, a surveying station was realised in a well bored for this purpose in the urban area of Bari. The monitoring started in 2004, using probes equipped with sensors of piezometric head, temperature, specific electrical conductivity, pH, dissolved oxygen and Eh. The detailed characterization of vertical variability of flow velocity has been realised with tracer tests realised in the well, using a fluorimeter. The sampling of groundwater and the laboratory analyses were realised to complete the activity. The whole data set are analysed highlighting the peculiarities of the selected karst aquifer and of groundwater quality degradation.